The invention relates to a supporting disk for a supporting disk bearing arrangement of an open-end spinning rotor, the supporting disk comprising a base body connected with a shaft, the base body comprising a supporting ring made of plastic, and also comprising a ring-shaped fitting made of plastic, the outer circumference of the fitting forming a bearing surface for a shaft of the open-end spinning rotor, the inner circumference of the fitting being joined to the outer circumference of the supporting ring.
The invention relates further to a process for the manufacture of a supporting disk for a supporting disk bearing arrangement of an open-end spinning rotor, the supporting disk containing a base body comprising a supporting ring made of plastic, and a ring-shaped fitting also made of plastic which is joined to the outer circumference of the supporting ring.
A supporting disk is known from German published patent 41 36 794 C2 which discloses a ring-shaped fitting made of elastomer material and a supporting ring made of plastic, which has a modulus of elasticity of between 7000 to 13000 MPa. Polycarbamide is the material suggested for the supporting ring, and for the fitting, elastomer polyurethane. Details of the modulus of elasticity of the material used for the fitting are not given in the above named printed publication.
It is an object of the invention to provide a supporting disk and a process for its manufacture which facilitate good operational reliability and cost-effective construction.
This object is achieved according to the invention in the case of the supporting disk in that the modulus of elasticity of the plastic material of the supporting ring is at least ten times the modulus of elasticity of the plastic material of the fitting.
In the case of the process for manufacturing according to the invention, the object is achieved in that the supporting ring and the fitting are each made in a separate first injection mould procedure, whereby the supporting ring and the fitting are fused together in a second injection mould procedure.
Due to the above-mentioned ratio between the moduli of elasticity, the requirements arising from a design for a supporting disk (sufficient rigidity to provide steady operation, sufficient flexibility to provide a good damping function in relation to the shaft) can be reconciled. The base body is rigid enough to guarantee a steady running without fluttering. The fitting is elastic enough to effectively take the impact of the shaft of the open-end spinning rotor, but rigid enough to avoid any excessive flexing work. Despite the low manufacturing costs of the supporting disks, which are largely made of plastic, a good operational function and damping effect are thus maintained.
Under the modulus of elasticity within the invention being presented is understood the interrelationship between the increase of tension and the increase in extension of a rod during unhindered cross sectional deforming under tensile load (DIN 53 457).
In an advantageous development, thermoplastics with differing chemical structures are used for the supporting ring and fitting. Thermoplastics are easy to process and facilitate a cost-effective production.
In another advantageous development, a duroplastic is used for the supporting ring. Duroplastics are also easy to use, for example in a two-component injection-molding process. A thermoplastic or another easily processed plastic could be used for the fitting.
It is advantageous to use plastics capable of being injection molded for the supporting ring and/or the fitting. Thermoplastics in particular come under consideration; they are very suitable for a simple injection-molding process.
In an advantageous development, the supporting ring and the fitting are joined together by frictional connection. A supporting disk with a high operational reliability is thus achieved in a simple manufacturing process.
It is advantageous to join the supporting ring and the fitting by means of contraction of the plastic of the fitting. Such contraction can, for example, occur when a thermoplastic is solidifying, whereby the extent of the contraction depends on the material used.
In a further advantageous development, a material interconnection is made between the plastic of the supporting ring and the plastic of the fitting. Such a material connection can be achieved by means of a melting of the adjoining areas of the plastic of the supporting ring and the plastic of the fitting. It is hereby advantageous when the plastic of the fitting has a lower melting point than that of the plastic of the supporting ring.
In an advantageous development, the supporting ring comprises a profiling which interlocks with a counterprofiling of the fitting. This interlocking can be used instead of or in addition to the frictional connection or the material connection. The profiling and counterprofiling can also be made in a simple way in an injection-molding process, whereby however the component which is first injected must be placed in a second injection mould for the subsequent injecting of the second component.
In an advantageous development the base body is completely formed by the supporting ring, so that the base body is made entirely of plastic.
In another advantageous development the base body comprises the above-mentioned supporting ring and a hub made of metal, preferably aluminum, which is joined to the supporting ring. The metal hub ensures a solid securing to a shaft of the bearing arrangement and thus results in good operational reliability.
It is hereby advantageous to join the supporting ring and the hub by frictional connection.
The joining can be done in an advantageous way by contracting the plastic of the supporting ring.
In an advantageous development the supporting ring and the hub can have a profiling and a counterprofiling, which, in addition to or instead of the described interconnection, facilitate an interlocking connection between the hub and the supporting ring.
In the process of the invention, the ring-shaped fitting and the supporting ring are each made in a separate injection-molding process, whereby the fitting and the supporting ring are joined together in the second injection-molding process.
It is hereby advantageous when the fitting is made in a first injection-molding process and the supporting ring in a second. It is also possible instead to proceed in reverse and to make the supporting ring first and then the fitting.
In an advantageous development, the second injection-molding process follows the first one after such a short time interval that both the fitting and the supporting ring have sufficient temperatures to enable the melting of the two plastics. The component first injected still has a high temperature, which lies just below the flow temperature. The component first injected is heated in the area where it comes into contact with the liquid plastic of the second component when this second component is injected into the mould. This has a particular effect when the flow temperature of the component injected second is higher than the flow temperature of the component injected first. Due to this advantageous process, the plastic of the fitting and the supporting ring are fused together well in the areas where they come into contact.
In an advantageous development the supporting ring and the fitting are made in the same injection mould. This simplifies further the manufacturing process. The injecting of the supporting ring and the fitting can be carried out to advantage when the plastic material for the fitting, heated to a free-flowing temperature, is injected into an injection mould. Then a mould core, with which the inner circumference of the fitting, now a little solidified, comes into contact, is removed in axial direction from the injection mould. The plastic material for the supporting ring, heated to a free-flowing temperature, is injected into the injection mould, whereby the injected material comes into contact with the inner circumference of the fitting, so that the fitting and the supporting ring fuse together by melting.
When the base body is to be provided with a hub, this is then placed in the injection mould. When injecting the supporting ring, the plastic material of same, heated to a free-flowing temperature, is injected onto the outer circumference of the hub, so that a strong connection is made.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.